The present invention relates generally to the art of hydrogen cooled generators and, more particularly, to a filter system for a hydrogen cooled generator.
Some power plant systems, for example certain nuclear, simple cycle and combined cycle power plant systems, employ hydrogen as a coolant for generators, which, during operation, produce large amounts of heat. Hydrogen's high heat capacity, low density and ability to reduce windage losses improves the output of the electric generator and the efficiency of the overall system. These properties make it desirable to maintain a high level of hydrogen purity within the generator. However, maintaining purity of the hydrogen in these generators is typically costly. Some power plant systems remove hydrogen via a scavenging system that extracts a portion of a mixture of gases from within the generator or drain enlargements, vents the portion of a mixture of gases to the ambient and replaces it with clean hydrogen.
Hydrogen cooled generators often include a seal oil or lubricant drain system that includes a detraining tank. The detraining tank allows any entrained hydrogen to escape from the lubricant. After the hydrogen is removed, the lubricant is re-introduced to the generator. In operation, the lubricant flows along rotating components of the generator and picks up hydrogen before passing into the detraining tank. In the detraining tank, the hydrogen escapes or rises from the lubricant. The lubricant accumulates and eventually flows over a standpipe and passes towards a recycling tank.
Hydrogen is circulated through the generator for cooling, and this hydrogen can pick up various contaminants that can reduce its purity levels. In some cases detrained hydrogen may also be recycled and reintroduced into the generator, and this hydrogen can also become contaminated. It is desirable to maintain a high purity level of hydrogen, and typically this purity level is measured by a hydrogen sensing system. If the purity level drops below a desired threshold, some hydrogen may be purged and clean hydrogen added to bring the overall purity level back into the desired range.
Hydrogen samples are typically obtained from various parts of the generator. For example, samples from the high and low pressure areas of the generator and the detraining tanks may be obtained. The sampling devices used are highly sensitive devices that can be easily contaminated by non-hydrogen elements in the gas stream. For example, lubricant may be present in gaseous or liquid form in the hydrogen sample. This lubricant can contaminate the hydrogen sensors and render them inaccurate or inoperable.